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    <script>
        //求出1/1-1/2+1/3-1/4…..1/100的和          var i=1;



        var i=1,j=1,sum=0
        for(;j<=100;j++){
            if((j%2)){
                sum+=i/j
            }else{
                sum-=i/j
            }
        }
        console.log(sum)
    </script>
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